B5 | Enzymes

• Enzymes are:

  • Catalysts that speed up the rate of a chemical reaction without being changed or used up in the reaction
  • Proteins
  • Biological catalysts (biological because they are made in living cells, catalysts because they speed up the rate of chemical reactions without being changed)
• • Enzymes are specific to one particular substrate (molecule/s that get broken down or joined together in the reaction) as the enzyme is a complementary shape to the substrate
• Investigating the Effect of Temperature on Amylase

  • Starch solution is heated to a set temperature
  • Iodine is added to wells of a spotting tile
  • Amylase is added to the starch solution and mixed well
• • Enzymes are specific to one particular substrate(s) as the active siteof the enzyme, where the substrate attaches, is a complementary shape to the substrate
  • This is because the enzyme is a protein and has a specific 3-D shape
  • This is known as the lock and key hypothesis
• How enzymes work

  1. Enzymes and substrates randomly move about in solution

  2. When an enzyme and its complementary substrate randomly collide - with the substrate fitting into the active site of the enzyme - an enzyme-substrate complex forms, and the reaction occurs.

  3. A product (or products) forms from the substrate(s) which are then released from the active site. The enzyme is unchanged and will go on to catalyse further reactions.
• Enzymes & Temperature: Extended

  • Enzymes are proteins and have a specific shape, held in place by bonds
  • This is extremely important around the active site area as the specific shape is what ensures the substrate will fit into the active site and enable the reaction to proceed
• Effect of temperature on enzyme activity

  • Increasing the temperature from 0⁰C to the optimum increases the activity of enzymes as the more energy the molecules have the faster they move and the number of collisions with the substrate molecules increases, leading to a faster rate of reaction
  • This means that low temperatures do not denature enzymes, they just make them work more slowly
• Enzymes & pH: Extended

  • The optimum pH for most enzymes is 7 but some that are produced in acidic conditions, such as the stomach, have a lower optimum pH (pH 2) and some that are produced in alkaline conditions, such as the duodenum, have a higher optimum pH (pH 8 or 9)
• Enzyme substrate specificity

  A) complimentary

  B) catalyse

  
• • Enzymes are specific to one particular substrate (molecule/s that get broken down or joined together in the reaction) as the enzyme is a complementary shape to the substrate
  • The product is made from the substrate(s) and is released

  A) substrate

  B) active site

  C) enzyme

  D) products

  
• • Enzymes are specific to one particular substrate(s) as the active site of the enzyme, where the substrate attaches, is a complementary shape to the substrate
  • This is because the enzyme is a protein and has a specific 3-D shape
  • This is known as the lock and key hypothesis
  • When the substrate moves into the enzyme’s active site they become known as the enzyme-substrate complex
  • After the reaction has occurred, the products leave the enzyme’s active site as they no longer fit it and it is free to take up another substrate

  
• How Enzymes Work

  1. Enzymes and substrates randomly move about in solution
  2. When an enzyme and its complementary substrate randomly collide - with the substrate fitting into the active site of the enzyme - an enzyme-substrate complex forms, and the reaction occurs.
  3. A product (or products) forms from the substrate(s) which are then released from the active site. The enzyme is unchanged and will go on to catalyse further reactions.
• • Enzymes are proteins with specific shapes.
  • The substrate must fit the enzyme's active site for reactions to occur, highlighting the importance of shape specificity.
  • Enzymes function best at their optimal temperature.
  • Excessive heat can denature enzymes, breaking bonds and altering their shape.
  • Substrates cannot bind to denatured enzymes due to the loss of active site shape.
  • Denaturation is irreversible, permanently halting enzyme activity.